Oscillation-current method and apparatus.



E. F. NORTHRUP. OSCIILLATION CURRENT METHOD AND APPARATUS.

APPLICATION FILED NOV.25. I916. I 1,286,395, Patented Dec. 3, 1918.

2 SHEETS-SHEET 1. FIG. 1 2'76 2 2762.5

A N A N W A N 3 311 uemlioz E. F. NORTHRUP.

OSCILLATION CURRENT METHOD AND APPARATUS. APPLICATION FILED NOV-25,l9l6.

1,286,395. Patented Dec. 3, 1918 2 SHEETS-SHEEN 2.

E] m uem coz the pool as resistor and inducing circumferone illustrationin that art, among the vari-' UNITED STA S PATENT OFFICE.

sown; r. 'nonrnnur, or rnmcnron, NE JERSEY, ASSIGNOR To THE AJAX METALcomrm, or PHILADELPHIA, PENNSYLVANIA,- A CORPORATION or PENNSYL- VANIA.

OSCILLATION-CU'BBENT METHOD AND APPARATUS.

' Specification of Letters Patent.

Patented Dec. 3,1918.

Application filed November 25, 1916. Serial No. 133,474.

To all whom it may concern:

Be it known that I, EDWIN F. NORTHRU'P, a citizen of the United States,residing at 30 Wiggins street, Princeton, in the county of Mercer andStateof New Jersey, have ining through a gap is contrasted with the.forced frequency directly produced by altern'ators.

A further purpose of my invention is to transfer energy from place tolace by electrict currents having natural equency and to transform theenergy into' heat at the place of intended use. a

A furthempurpose is to make the resistor, which is to be heated ortreated or to be worked while hot the secondary of an inclosing oscillation coil primary or primaries, discharging a condenser orcondensers through this primary and a discharge gap to inducecurrents'of corresponding period within the resistor. I purpose applymgmy invention to the electric furnace art, among. others, using the bodyof ential flow of electric current about it, without theintermediationof a magnetic circuit such as is threaded through thepoolor through a connecting tube in existing induction furnaces.

A further urpose is to charge condensers from multip ance coils hav ng acommon magnetic path, preferably a common ,core,, protecting thegenerating. ap sive-current ow and throughthem transferring to anotherphase or other phases, ener Further urposes will a ar inithe se'cification and in the claimg iiereof. p

I have referred to illustrate my invention chie y diagrammatically, inview of the broad character of the invention, and have applied it to butone art and to but ous arts and many-forms in which itma be carried out,selecti therefor an art w 'ch is important and a orm which is practical,

frequency of a freely oscillating electric system from a'condenserdischargase currents through inductaratus by them from exceswhich wouldotherwise be uselessly emp oved.

efiicient and simple, in which my invention has high commercial utilityand which at the same timeillustrates the principles of my invention toconsiderable advantage.

Figures 1 and 2 are diagrammatic views used in discussion of theprinciples of my invention.

Figs. 3 and 3 are diagrammatic views of connections which may be used inapplying my invention;

in Fig. 3.

Figs. .5, and 6 are diagrammatic views showing in a more or lesshypothetical way the directions of fiow of induced currents ofelectricity and of a molten oscillation re sistor when my invention isapplied to furnace operation.

Fig. 7 is a diagram used-in discussing the assistance which can be givenone phase from the other in-two phase application of my invention.

Figs. 8 and 9 are a vertical elevation through the pool and a top planview respectively of a structure by which I may apply my invention toinduction furnace uses.

Figs. 10 and 11 are diagrammatic views showing application of'myinvention to ingot mold and ladle use respectively.

In the drawings similarznumerals indicate like parts.

I My invention applies OSCllltltOlY electriccurrents to the heating ofconducting material performing a stirring function also by the samecurrents when the mass is a molten and in the processes and mechanism bywhich these principles are utilized in the particularv artfrom which Ihave taken my illustration.-

Fig. 4 is a-mixed diagrammatic and sec-' tional view of a portion of thecircuit shown The broader form or my invention is claimed by me in aco-pending'application, Serial No. 192,049, filed September 19, 1917,for method and apparatus for electric heatin by high frequency currents/he introduction of inductance into the circuit of a constant speedalternator. transmission line' under forced vibration causes thecurrent'to lag *in phase behind the electro-motive force, and capacityso introduced causes the current to lead in phase. The

preponderance of induction over capacity,

both in the line and in the coils of existing inductionjapparatusapplying heat,has reduced the power factor making it prohibionly notrequired but even injurious.

If, on the other hand, electric energy be stored in a condenser and thelatter be then allowed to discharge itself through a closed circuit, theelectricity oscillates back and forth like a pendulum until the energystored in the condenser is finally dissipated in electric radiation andin heat. The inductance in such a circuit does not affect the totalenergy transformed, only the natural frequency, the time within whichthe vibrations will cease, the damping factor and the number ofvibrations. In this it is comparable with the mass of a ball swinging atthe free end of a spring whose opposite end is fixed. There is nodissipation of energy in this mass and its increase merely alters thenatural period of the vibration, the time within which the spring comesto rest and the, number of vibrations of the spring.

' If the capacity and inductance be large,

the fraction of energy dissipated in radiation is negligibly small. Themovement of electricityin the circuit constitutes a natural, unforced orfree vibration having a period Since T-should be less the. the period ofthe alternating current supp y and in pracas tice is therefore limited,the product of LXC must be keptwithin limits. This can very readily bekept within required limits for any total values of capacity and inducIt might benoted thatthe currents in the oscillation resistor correspondto those in the oscillation coilin period and follow the fluctuations ofthe oscillatory currents even though they be not themselves of freevibra ,tion.

The only points or places in such a free e cillation circuit where heatis dissipated are where there is 'ohmic' resistance or where there is aninductively coupled circuit hav' ing ohmic resistance, such as. a solid,liquid 01 plastic body of conductin material, or

container or holder therefor ormin asecondary to such a free oscillationpr1mary.

ltf follows that conductors which lead from the condenser to theoscillation coil at the place where it is required to convert be wellunderstood from this figure.

L, and L washes the energy stored in the condenser intoheat may be quitelong and may have considerable inductance without wasting energy objec-vtionably in heat during this transmission, provided these conductorshave small ohmic resistance. Practically, as well as theoretically,therefore, energy stored in a condenser can be transmitted aconsiderable distance from the location of the condensers with low heatlosses, and there converted almost ,wholly into heat. This conversionmay not denser'and the voltage applied in charging it. The power is thendetermined by the number of times the condenser is charged to thisvoltage and discharged per unit of time.

The inductance of the circuit, the resistivity of the metal constitutingthe secondary coupled circuit or resistor and the closeness of thecoupling have no efiect upon the power generated and, theoretically, no

efiect upon the power delivered to the metal.-

-Where the available voltage is sufficient to charge the condenserdirectly from it, no transformer is required between the supply and-thecondenser and I have shown s ch' a construction in Fig. 1. The theorywig single phase alternating current circuit vis shown having-sides A,N. The condenser to be charged is shown at C, the oscillation coil,through which the'condenser discharges at O, the inductance of the twosides of the circuit at L and L and L L and a discharge gap at G. Theseinductances are intended to represent the entire inductance of eachsideof the circuit and are-divided for convenience in the laterdiscussion.

-Tlie energy stored at each charge is 1/2 CVK When the discharge gap Gbreaks down, the energy will surge in the oscillation circuit until 1tis all dissipated in radiation andheat, for low frequencies chiefly inheat.

The means .of dissipation are as follows:

1-Dielect'ric loss in condenser. 2- I+ R loss; in discharge gap G} 3 -IR loss in line, where R is theomm reslstance of the linepossessinginductance 4"TI2R, loss where R is the ohmic resis tance orits equivalent of that portion of of energy utilized in radio telegraphyand is quite negligible for low frequencies.

' 6Losses 1n the transformer D which feeds the oscillatory circuit.

It is indifferent whether R is a resistance located in theoscillatorycircuit or whether it is a resistancein an inductivelycoupled circuit, 2'. e., in the oscillation resistor, or the sum ofthese. And because the secondary circuit constitutes buta single turnwithin the mass and the inducing circuit has several turns, themagnitude of the current in the. oscillation resistor is correspondinglygreat.

In speaking of the mass I desire to make clear that, though in some usesof my invention the oscillation coil may operate upon a thick mass, theshape may vary widely according to the application intended and may be,for example, a mereshell of cylindrical or other shape, solid, in pasteform, molten or normally liquid.

It will be noted that the oscillation coil 0 inthe illustration forms apart of two circuits. It is part of the secondary alternating circuitfor charging of the condenser and also constitutes an oscillationprimary .in the discharging circuit for the oscillation resistor as asecondary.

In the effort to transmit. the energy stored in, potential form in thecondenser to the conducting material heated with maximum efiiciency, itis indifierent, within wide limits, what maybe the natural frequency ofthe oscillatory circuit. The eificiencv which wel'wish toget is where pis power dissipated and held as heat in the oscillation resistor and Pthe powersupplied at' the primary terminals of the Hush rmer. f

To obtain high efliciency the following losses must be small .ends ofthe oscillation coil 0, measured at e in Fig.- 1 can be keptcomparatively low. This will facilitate insulation between the coil andits secondary.

With each surge of the oscillatory current through the coil circuit,there will be a tendency of the supply current to short circuit'throughthe ionized air acros the dis- 1,Dielectric loss. '(Low frequency ofos-- sired to charge the condenser, the circuit will more usually be asindicated in Fig. 2, where the supply circuit A, N, is transformed at Dand the condenser is charged from the; secondary transformer connectionsa, 1. While the short circuiting of the supply, (here taking place inthe secondary) across the discharge gap, can still bacontrolled byprimary inductance, or by special provisions for blowing or vacuum atthe discharge, it is more desirable to control it by inductance in thatportion of the circuit between the discharge gap and the transformersecondary, indicated diagrammatically at Z, 2,. The discussion of Fig.is then applicable to this form also with the change in symbols from A,N, to a, n, and L L to Z 1,. In Figs. 1 and 2 the oscillati on coil maybe placed in the discharge pable of easiest clear explanation.

Because transformers will be required usually to .ste p-up the voltagefrom that available to the much higher voltage under which my inventionbecomes most eflicient, I have shown transformers here, the systembeingpracticable wherever two phase current may be obtained. Thetransformers can be omitted where the commercial current is of suitablevoltage. 0

.The two phase primary circuit has sides A' andB and neutral N andsupplies transformers I) and E. The secondary of transformer D isconnected with one side each of discharge gap G and condenser Q byconductors a, a and a and with the other side of the discharge gap andcondenser by conductors, n, n, 72. n and n. Likewise the secondary oftransformer E is connected with the two sides of discharge gap G andcondenser C by conductors b,'? ,.b and n, a 11. 'n and n3.

The windings L and L, respectlvely of a reactance. coil L are placed inseries with the discharge gaps G and G, andtheir connections n, n and n,n; and the oscillation coil 0 may be placed in the charging circuit inthe common connections n n therefor, or coils may be placed in thedischarge gap connections a, b, where distant location of the coilsmakes this desirable.

There are condenser charging expedients, at present well known, which donot require stated.

alternating currents. Since they are in the nature of makeshifts orubstitutes and, so far as they are successful, are electricalequivalents of the alternating current charging source, I desire to beunderstood as in cluding them within my claims where the latter includealternating current and these substitutes can be used in thecombinations Fig. 3* shows other connections suitable -to use with alocal charging circuit includ ing the condenser or condensers and theindu'ction coilor coils and an oscillation coil or coils, thedischargegap beingpermissibly placed at any point in the discharge circuit.

,If no transformer be neededlt'o vary the voltage of the alternatingsupply circuit, the sides A, B would beconnected directly to conductorsa and b and the neutral to n and n In the use of multiphase supply itwill be noted that the'discharge from different c0ndensers will occur atdifferent times, since they are charged by currents of difierent phase.

In any condenser operation, if short cir- .cuiting of an alternatingcurrent, condenser charging circuit through the condenser discharge gapor gaps be prevented by the in troduction of inductances in this supply(whether transformers be used or not) there is a considerable advantagein the use of multiphase currents since they make it possibleito use acommon core for the inductance co1ls in thedifferent phases, returningto the other phase orphases energy which would otherwise be spentuselessly in the discharge gap, if the useful transfer of energy fromphase to phase were not provided.

' This transfer of energy from phase to phase-between inductances inmultiphase circuits can be used with greatadvantage not only in the artsinwhich an oscillation coil is used to apply heat to an oscillation re-'sistor, which forms part of my invention claimed herein, but boththe-process and apparatus are also applicable to other arts,

where the heating effect, is not of importance, such, for example, as inthe arts of wireless telegraphv and telephony, and this subject matteris intended to be'cl'aimed by me as-broadlynew.

Application of this inductance coil energy transfer between phases tothe remain- (her of my invention herein will be clear from Fig. 3, wherethe two reactance coils L L are-wrapped about a common core L As aresult, when the voltage in phase A, I ig. 7), rises to'some such pointas p, charging. the condenser G',-the'inductive action. of the coil Lupon the coil. L to some extent affects thevoltage, (or the phase of thevoltage) being impressed by phase B,

through coil L upon condenser C The gap G now breaks-down and thesecondary at D-is put on short circuit through the gap G. The rush ofcurrent which tends to follow, magnetizes the core, and the energyrepresented by this magnetization is in 'part transformed to the coil Lhastening or retarding, (according to the relative directions of thewindings on the core) the rises of voltage being impressed uponcondenser C The same action takes place when condenser C is beingcharged and when gap G breaks transformers D and E, confining them tothe i;

circuit shown in the lower part of the figure through the oscillationcoil and discharge gap.

In operation, the multiphase electro-motive forces are impressed uponthe primaries of the two transformers D and E and the condensers. C andC are charged through reactance coils L and L and with the particularconnections shown, also through oscillation coil 0, until their capacityis reafihed with the discharge gap adjustment use As each discharge gapbreaks down the oscillatory currents .will surge through the oscillationcoil 0, acting as a primary and will induce oppositely directed currentflow I in the resistor W, formin the oscillation secondary, the currentflow 1n the oscillation secondary being in substantially parallel planesor strata to that in the inducing oscillation coil.

The successive chargings of the condenserswill alternate, as will .alsotheir discharges,

at irregular intervals dependent upon the capacities of the condensers,the applied voltage, theseparation of the discharge gap and possiblyother variables, a rapid series of heating impulses which also have astirring vact1on. proportlonate to the energy input ends at G and G areprovided with nozzles G, and (it capable of operation with either yacuumor air pressure, to red ce thearcmg, and the bar Gr carrying contacts G,and Gr is adjustable as by screw G operating in a support G I haveillustrated my invention'by application to an electric inductionfurnace, and will describe its use in connection with the particularfurnace shown in Figs. 8 and 9, to which the principles are welladapted, but which is described by way of illustration and notlimitation.

I-would expressly point out that though there is patentable novelty inthe a plica- 'tion of'the broad invention to'the rnace art, and to theparticular furnace illustrated, electric furnace operation is one onlyof'various uses ofthe broader invention.

Successful furnace operation requires rapid transfer of heat betweenthemetal most actively heated and the remainder of the metal. This must beby conduction or by circulation or both. In existing gas and cokefurnaces, conduction and Joule effect within the pool are relied uponand have proved fairly satisfactory. In the various electric inductionfurnaces heating the metal in channels connected with the pool, theopportunity for conduction is poor and circulation by pinch effect,motor effect or Joule effect is largely relied upon to obtain andmaintain substantial uniformity of temperature- Moreover, in most atleastv of these channel induction furnaces, the more highl heatedmetalmust be removed from the c annel to the pool rather quickly to avoidoverheating within the channel. This is particularly true with suchmetals, as

brass, as contain easily vaporizable contents,

. whose vaporization will vary the cross section of or break the(secondary) channel c rcuit and also causea change of proport1on ofcontent. The narrow range of temperature available in such a metalmaybe.

seen from the fact that brasses melt at 940 C. and zinc, begins'tovaporize from brass at 1090 o;

For furnace operation my invention possesses the advantage of inducingclosed currents of electricity in the furnace or crucible pool, asdistinguished from utilizing a channel or other outlying path. Theoscillation coil may conveniently surround the. pool and lie in anydesirable plane or series of parallel planes inducing current'flow inthe pool in planes parallel to its own. It is most convenient to placeit horizontal with the crucible furnace shown.

The freedom from channels and other outlying containe s of molten metalmakes my furnace'more nearly comparable with existing gasor coke-heatedcrucibleffup naces and the position of the induced cur rent path withinthe metal still further helps in unifying the temperature of'the pool.

Though theoretically the induced currents the heat conductivity andother character'- istics of the material being heated, the quanwithinthe pool are distributed over a large. part of the body of the pool invclosed conducting lines, skin effect causes the curcurrent, with theresult that this current flow within the oscillation resistor, can bemade great enou h to develop useful pinch contraction of t ecurrent-carrying metal, giving I commercially practical stirring, whichis articularly'useful with the circumferential heating of the pool by tecurrent in it or in the crucible walls. or all practical purposes pincheffect has prevlously been regarded as confined to passages of smallcross section used in connection with pools. A

The stirring movement lsdue to combined pinch and Joule effects and isquite noticeable I in the molten pool when the oscillation cur-' rent ispassed through the surrounding coil. Its direction, however, cannot be'so accurately determined from observation. It probably takes placeswithin radial planes through the coil axis, with greatestconcentration'at about the middle of the coil height and an inward andupward direction there, about as indicated in Fig. 6. The center ofthepool lifts'above its normal level, which would confirm this.

Since the metal ofthe pool is heated along the outside throughout thewhole of its vertical height, the oscillation coil stirring effectuallymixes the metal. The concenof the top of the pool obtained by thiscirculation, at the point where fresh charge is put in, tends also toequalize the temperature reducing the temperature difference as thecharge is melted.

I .have shown how effective stirring may be obtained. The question ofits need is dependent so much upon the speed of heating or meltingrequired, the heat losses planned,

tity of fluid being handled, the shape of the pool, the range ofdifference in temperature permitted by the intended use and other where1 but a very small energy input per 180 tration of relatively hot metalat the center factors determined, by the character of involume .isrequired, for the temperature results sought,lthere will be little ornooscillation stirring: On 'the other hand, an induction furnace, meltingmetals and planned to secure maximum output will utilize a large inducedcurrent density and will need and obtain corresponding stirring benefit.Obviously additional stirring can be employed if special circumstancesrequire it, to at this is neither necessary nor desirable under normalcircumstances.

Though the stirring-effect is secondary in my view to the heating effectof the oscillation current, and may be omitted or disre- 1:5 garded, asshown, in some applications of my invention, it is not for that reasonunimportant, as the stirring may be proportionedto the need by varyingthe, current density, enabling the designer to so'proportiontheoscillation current and volume or shape of the pool of the crucible orfurnace as that the conduction, Joule effect and oscillation stirringwill maintain sub stantially uniform 'temperatuie conditions throughoutthe body of the furnace, and I purpose claiming this oscillationstirring broadly as applicable not only to induction furnaces, but tothe stirring ofany molten or otherwise liquid electrically conducting 80mass. r

In the furnace illustrated in Figs. 8 and 9, I have shown a cruciblefurnace having the crucible fixed atthe time of use and with bottomoutlet, because the simplicity, re-

liability, economy in labor and operation and low cost of this form makeit the most desirable and because notwithstanding the ideal character ofthis furnace, induction heating has not been previously applied to itsuccessfully. 1 The crucible 10 is removable for cleaning andreplacement and may be removed for pouring by lifting mechanismengaging.

with the crucible and already known in the furnace art. This issuggested sufiiciently for present purpose by holes 11. I prefer to givethe crucible a bottom outlet "12 for pouring purposes placing itoff-center in insulated from the crucible.

order to giveas muchroom as possible. for

charging. The crucible is formed of any suitable refractory, which maybe an electrical conductor oranon-conductor as suits the needs of theinstallation or.the preference of the engineer. It is most desirably ofsufficient mechanical strength to permit themetal to be chilled initwithout breakage. The tapering of the sides of the 1nterior cruciblewall reduces the danger of breakage. Where the crucible is itself. aconductor, the lines of induced current How will of course-take placelargely. if not exclusively in the walls bf the crucible and the heatingof the pool will be by conduction from these crucible walls.

v The cover and plug-operating mechanism The bath or pool content may bea conductor or non-conductor of electricity, normally liquid, or ofvpaste consistency or fused, as barium chlorid,-and may be undertreatment itself or be used in treating other materials as in tempering,for example).

The outlet 12 is closed by a refactory plug 13, of any suitablemateriahsuch as carbon, which I insert. through the cover 11 and thebody W of the pool. The outlet and plug are placed off-center so as togive room for charging through any opening in the cover, closed by a gap15. The plug can be withdrawn for pouring purposes, and I show one meansfor this. The wheel 16 operates a sleeve 17 which turns within a bracketsupport 18 secured to the cover. Relative vertical movement is preventedby set screw 19 and annular sleeve groove 20. Lost motion istaken up byspring 21. The interior of the sleeve is threaded to'engage with a screw22 which is formed at its lower end as a socket at 23 to receive theupper end of the plug 13, the cpupling being completed by a pin 24. Thescrew is kept from rotation by engagement of a non-circular part of thesocket with thewalls of a 001: respondingly shaped hole in the cover, asat 25.

can thus be lifted without disturbing the plug and the crucible can beremoved with nearly the same freedom as if intended to be lifted forpouring, known in the furnace art.

The crucible rests upon a heat insulating block26 supported by a base 27for both of which alberene stone is well suited. The block and base restupon stone-legs 28 and are cut away, as at 29 and 30, below thedischarge opening 12, to allow free flow of- :metal through the blockand base to any, -mold, not shown.

The removability of the crucible from the body of the furnace,'whetherrequired for pouring or not, requires that the furnace coil O shallbeseparately mechanically supported, and that itshall be particularlywell I have indicated the support and insulation as com- 116 [prisingcylinders '31 and 32, for. which alberene and quartz, respectively arewell suited. Oscillation coil 0 is preferably formed of edge-woundcopper strip, nickel plated to prevent oxidation and is mounted me uponor about the outer cylinder. Its windings are spaced and insulated by anasabestos cord 33. I

Both ofthe cylinders are set within a recess or recesses shown at 34. inthe block- 26, and may be made removable from the base for convenience.k The cylinders and coils are placed within an outer insulatingcylindrical casing 35 from whlch they, are preferably spaced, as

at 36, to rovidefor a surrounding insulation 37, w ich I haveillustrated as sea-sand and which may be loosely poured in place afterthe parts have been seated.

The cover 14 fits down into the outer casing as at 38, far enough toprevent it from side movement, and the intended position to bring itsplug opening in line with the outlet in the crucible is fixed by a pin39 or other keying means.

' Outside current connection is best made from below, on account of thehigh currents intended to be passed-through the oscillation coil 0 and Ihave provided for this conveniently by holes 40, 41 within whichconductor rods 42,43 are inserted,

the connections with the two ends of coil being shown as formed by ins44, threaded into holes in the rods an connected with the coil ends byconductors 45and nuts 46. For convenient access. to drill the holes 44through which the pins pass; I have rovidedholes 4:4 in the outercasing, which atter are subsequently plugged. The lower ends of theconductor-rods are protected by tubing, preferably quartz, shown at 47,

48. The tubing is surrounded by a.

grounded casing 49 in each case. v

Because :of the high voltage utilized by the furnace-and to avoidpossibility of injury therefrom, I have ounded all of themetal..pai'ts,rincluding t e yoke or bracke't at the top, and liftingmechanism for the plug rod and have surrounded the furnace ounded cage,comprising, as shown, top an bottom rings 50, 51 and connecting bars 52,to an one of which themetal arts and grounded casing may be connectedThe process and apparatus abovegenerallydescribed when applied toheating and stirring molten metal in a furnace, as will be seen from themechanism illustrated, secure results closely approximating the perfectfurnace.

It will-be evidentfthat the theory of op-' eration, process and referredstructures used as lllustrations erein, will suggest many and variousforms in which my inventlon may be utilized by the public to heat orheat and stir. liquids or molten metal, or for welding or forgingpurposes at temperatures lower than the melting point or barely reachingthe melting point and without stirring; and thatthe application of thesame or allied structures or processes to any sucli uses will embody myinvention,

whether additional inventive skill be re-' quired or not.

It is further evident that my invention has general utility in thetransfer of power for'various purposes utilizing the discharge from acondenser for the accomplishment of work at a considerableidistance.

The metal can be chilled in the furnace without breakage, develops no.cracks on "intermediate withdrawal of the crucible.

torily met before.

' mouth to prevent melting and can be melted in place from the solidstate.

The furnace is easy to fill and empt the molten metal can be drawn offfrom below the level of the metal, and there need be no movable partsexcept the stopper plug and the mechanism by which it is moved.

There is a marked economy in the labor required.

he inductive electric heating isclean and uses no electrodes. Myapplication of it produces no disruptive internal pressure orces and thepath of the current in the molten metal cannot be interrupted. The metalcannot be subjected to contamination from gasesand so large a mass ofmetal is in contact with the portion most rapidly heated that conductiongreatly assists the circulation in preventing any considerabledifference in temperature of different parts 85 of the 001, minimizingthe importance of circulatlon. There is no danger of vaporization ofconstituents having a low vaporization point, unless substantially theentire mass is overheated.

The types of the furnace otherwise best suited to carry out my inventionfacilitates heat insulation, sothat substantially all of the heatgenerated remains in.the metal.

The pool requires but little melted metal to operate well and can bestarted with turnings or even with more solid chunks of metal. Theentire charge can be emptied and a new charge started ,with or withoutCommercial charging frequencies can be used and the furnace 1s capableof highly advantageous use .on olyphase circuits, avoiding unbalancingof such circuits.

The primary voltage from the generator can be used where high voltagesare. available, avoiding. step-up or step-down transformers. V

l The ower'factor may be maintained substantially at unity and theefliciency markedly increases with the size ofthe furnace.

It is particularly suited for melting precious metals where therequirements are most exacting and have not been satisfac-' Closelyallied to furnace uses are those in which material in'a path or pool,whether electrically conducting or nonconducting is to be maintained hotor heated, but in which no melting or ore reduction ,,(such as might beperformed in the furnace illustrated) is required, and I have shown twodiagrammatic illustrations of such uses in Figs. 10; and 11 In Fig. 10an ingot mold I is provided with an -roscillating' heating coil Ofiforthe the metalyhot at the piping which has so seriouslyinterfered withtheuse of theentire ingot in steel'work ,Here the heating purpose ofkeeping is intended to be local only andthe stirring function may benegligible. p

In Fig. 11 a pouring ladle K is shown with a heating'coil O for thepurpose of keeping the metal in the ladle hot during the desirablesettling after filling the ladle and before pouring from it. Some slightstirring would be helpful here.

It will be evident that the several uses suggested are but a few of thelarge number to which the broad principles of my in-. vention areapplicable. The transfer of energy to the distance by oscillatorycurrents, the trading of energy between phases of a 'multi-phase currentand. the. induced heating effects from oscillatory discharge areseparately useful-.indifi'erent as well as in many of the same arts. Theheat-treatment of metal alone includes not only-the furnace treatment ofore and metal, but tempering, annealing, forging, solderlng, etc.

.In treating liquids I believe that I am the I first, moreover tousefully employ pinch from currents induced in a .pool or bathitself, asdistinguished from channel discharge into or through the pool or bath.

I recognize that, with the disclosures a com enser charged t erefrom andadapted to be discharged, a transformer primary in the discharge circuitfrom said condenser and a heating coil secondary in inductive relationthereto.

QaAn induction heating system comprising a primary alternating sourceofcurrent,

a transformer'connected therewith, a, condenser charged from thesecondary of said transformer, a heating oscillation primary in the.discharge circuit of said condenser and in inductive relation'to theresistor to be heated, and aninductance-coil in the secondary circuitprotecting aga nst conphasefan inductance coil in series with each 1denser discharge.

In apparatus utilizing oscillatory currents, a multiphase currentsource, con densers-. charged therefrom, "one for each phase-of thecharging current, thecoils hav- -mg inductive .relation to each other,and

connections for discharging the condensers fife." Iniheating".mechanism,.; an oscillation heating'eoii mductiye relation to themaenalgto be heated, a 'mu'lti-phase current.

mechanism com-' prism an alternatin current transformer,

neeaaee source, condensers charged therefrom, inductance coils in seriesw th the charging current, one in each phase and in inductlve relationto eachrother, and a discharge gap 10- cated. between the inductanceCOIlS and ductive windings in series with the charg-v mg circuit, one 1neach phase and having a common magnetic core and discharge gaps betweenthe windings and condensers for discharging the condensers through theoscillation coil.

6. In a heating system; an; oscillation heating coil in inductiverelation to the material to be heated, a multi-phase current I source,condensers connected with the 0scillation coil, discharge gaps fordischarging .the condensers through the coil and connections between thecurrent source and the circuit including the coil,condensers anddischarge gaps foi charging the condensers, said connections havinginductive windings about a commoiT core adapted to trade energy from onecircuit of said connections to another. \V 7. In a heating system,oscillation heating coil provision in inductive relation to the materialto-be heated, two condensers and two discharge gaps forming dischargecircuits through the oscillation coil provision, two charging circuits,one for each condenser and passing through windings upon a common coreproviding inductance and adapted to trade energy anda multi-phasecurrent source for said charging circuits.

8. .In an .alternatin current heating s stem, oscillation coil he ralityof condenser and discharge gap c1rcuits adapted to dischargetherethrou'gh, separate charging circuits for said condensers havingwindings in series therewith upon a common magnetic core and multi phasecurrent supply for the charging circults. v In an induction heatingsystem, a primary source of electric current, a transformer connectedtherewith, a rea'ctance coil connected in series with thetransformersecondary, a condenser charged from the secondary, adischarge gap across the charg- -ing circuit between the condenser andrecontainer thereinadapted to hold material 1n lflfllld form and freeoscillation current supp y for said coilating means, a'p u- 1 11. In aheatin device 'a source of electric current, a con enser c argedtherefrom, a discharge ap for the condenser and an oscillation 0011through which the condenser is adapted to discharge in inductiverelation to electrically-conducting material to be heated. g

12. In a heating device, a source of electric current, a condensercharged therefrom, an oscillation coil adapted to surround a liquid pooland connected 'inth'e chargin circuit and a dischar e gap across the conenser on the far side 0 the coil therefrom.

13. In a'heating and stirrin device, a container having a draining outet, a heating and stirring oscillation coil. thereabout, andfree-oscillation current supply for said 001 14. In a heating andstirring device, a container for an electrically conducting pool andhaving a bottom outlet, a plug for said outlet extending downthrough thepool and induction means setting u closed current paths in said pool forheating the pool and stirrin it.

15. n a heating device, atwo-phase current supply, two condensers, onecharged from each phase of the supply, two reactance coils, one inseries with each phase of the charging circuits, the'two coils having acommon core, a container for a pool, an oscillatlon 0011 in series witheach phase of the char 'ng circuits and surrounding the 001 anbreak-down discharge means for t e condensers, discharging in each phasethrou the oscillation coil.

16. n a'heatin device, an induction coil, a crucible inserti le into andwithdrawable from the coil and an oscillation current supply for theterminals of the coil.

17. In aheating device, a crucible having a draining outlet and directinduction means for causing closed lines of electric current flow withinthe content to heat it.

18. In aheating device, acrucible having a draining outlet, a plug forclosing. said outlet, (passing through the body of the pool, a con forcharging said condenser and means for discharging the condenser throughthe con-' ductor.

19. In a heating device, .a furnace adapted to contain a pool a d toremain fixed during use, in comblnation with a coil surrounding thefurnace and free oscillation current supuctor surrounding the crucible,a condenser connected with said conductor, means 21. In a' heatingdevice, an oscillation coil, insulation therefor, a crucible within thecoil and having an off-center draining outlet and free oscillationcurrent supply for the ter- 'minals of said coil.

22. In a heating device, a removable crucible having a draining outlet,a furnace casing from which said crucible is removable, a coil windingin-said furnace casing in proximity to the crucible and connections fortransmitting primary current through said coil to induce secondarycurrent flow in the crucible.

23. In a heating device, a crucible having generally cylindrical outer.contour and bottom outlet and adapted to contain a pool, a casing withinwhich the crucible is removably supported and a cylindrical coil windingwithin the casing close to-the opening for the pool.

24. In a heating device, a crucible, in combination with .an edge-woundcoil conductor surrounding the crucible. j 25. In a heating device, ahollow coil support, an edge-wound oscillation coil there about and acrucible removably supported within said support.

26. In a heating device, a base, a refractory annular insulationremovable therefrom,'a coil winding upon said insulation, an 95' about,the container to induce current flow in the container as a seconcary.

29. The process of charging and discharging condensers which consists incharging the condensers in parallel through moss in inductive relationto each other and in discharging the condensers through dis charge sparkgaps located between the reactances and the condensers.

30. The process of charging and discharg into electriecurrent havingnatural, as distinguished from forced frequency, in transmitting itto adistance in this condition by conductors and in transforming it at thepoint of use for heating urposes;

32. The method of uti izing electric potential energy at a distancewhich. consists in storing the energy in condensers, in dis-' chargingthe condensers through conductors extending to a distant point andthrough a conducting coil-located at that point and in inductivelycoupling the coil and the work at the oint of use for heating purposes.

33. he method of utilizing at a distance electric ener stored in acondenser which consists in c arging a condenser through a: localcircuit at one point. in dischargingit memes through conductorsextending to e distance point and in there utilizingthe oscillatorydischarge fromsaid condensers.

34. The we utilizing at e distance. electric potential ener stored in .acon denser which consists mcharg the com denser through a local circuitincluding an inductance coiland in' discharging fiiecondenser through adifierent circuit excluding the inductance coil and extending to adistant point, and there passing the'dis charge throu h'e-transformercoil and mi lizing the in uction from-sffllidmoilfor aproduction of heat within a meteriel adapt ed to heated EDWIN NOEL-H23;

